Solid acid catalyst containing platinum group metal component and method for preparation thereof

ABSTRACT

The present invention provides a concentration distribution for a platinum group metal component in a catalyst with which catalyst activity can be increased, and to provide a method for supporting a platinum group metal with which this concentration distribution can be achieved. The present invention is a solid acid catalyst that is made up of porous catalyst pellets exhibiting solid acid characteristics, and a platinum group metal component supported by these catalyst pellets, and that is used in an acid-catalyzed reaction, in which a quotient of dividing the standard deviation of the concentration in a platinum group metal component concentration distribution in the catalyst by an average concentration is 0.4 or less. The method for preparing this catalyst involves a step of preparing a support solution containing a platinum group metal as a cation, and a step of impregnating crystalline, porous catalyst pellets exhibiting solid acid characteristics with this support solution. The present invention also provides a method for isomerizing a hydrocarbon, wherein a solid acid catalyst is brought into contact with a hydrocarbon including at least 70 wt % of a saturated hydrocarbon component having 4 to 10 carbon atoms.

TECHNICAL FIELD

The present invention relates to a method for supporting a platinumgroup metal component with which a solid acid catalyst having highactivity in an acid-catalyzed reaction can be obtained, and to a solidacid catalyst obtained by this method.

BACKGROUND ART

Acid-catalyzed reactions such as alkylation, esterification, andisomerization are known in the chemical industry. Acid catalysts such assulfuric acid, aluminum chloride, hydrogen fluoride, phosphoric acid,and paratoluenesulfonic acid have been used in these types of reactionsin the past. However, a property of these acid catalysts is that theycorrode metals, which has meant that the manufacturing equipment had tobe made from expensive corrosion-resistant materials or subjected to ananti-corrosion treatment. Also, since in addition to the difficulty ofseparating the reaction substances after the reaction, a waste acidtreatment was usually necessary, the process entailed complicated stepssuch as alkali washing, and caused a serious environmental problem.Furthermore, it was extremely difficult to recycle the catalyst.

In response to these problems, there has been proposed a sulfuric acidgroup-containing solid acid catalyst obtained by bringing a hydratedoxide or hydroxide of a metal from Group IV of the Periodic Table intocontact with a sulfuric component-containing solution, then calcining at350 to 800° C. (Japanese Patent Publication 59-6181). This solid acidcatalyst exhibits a higher acid strength than 100% sulfuric acid (theHammet acidity function H₀ is −11.93). Because of its high acidstrength, this solid acid catalyst provides good catalyst performance ina wide variety of acid-catalyzed reactions, and furthermore has lowcorrosivity, separation of reaction substances is easy, there is no needfor waste acid treatment, and the catalyst can be recycled. As such,this catalyst is expected to supplant conventional acid catalysts inmany kinds of industrial reactions.

It is already known that a catalyst comprising platinum added to acatalyst obtained by calcining a zirconia gel containing a sulfuriccomponent exhibits good activity in hydrocarbon isomerization reactions(U.S. Pat. No. 3,032,599). As for methods for preparing a metal oxidecatalyst containing a platinum group metal and a sulfuric component,which are intended primarily for the isomerization of hydrocarbons, amanufacturing method that omits the calcining between the treatment witha sulfuric component-containing compound and the step of supporting aplatinum group metal, a manufacturing method in which the order of thetreatment with a sulfuric component-containing compound and thesupporting of a platinum group metal is reversed, and a manufacturingmethod in which the type of sulfuric component-containing compound ischanged have been disclosed in Japanese Patent Publications 5-29503,5-29504, 5-29505, and H5-29506. A method for preparing aplatinum-containing zirconia sulfate shaping has been disclosed inJapanese Laid-Open Patent Application 9-38494.

DISCLOSURE OF THE INVENTION

However, supporting the platinum on the catalyst was accomplished byimpregnation with a support solution comprising a chloroplatinic acidaqueous solution, and there-has been no particular discussion of theconcentration distribution of the platinum group metal in this catalystup to now, nor has it been known what distribution would be best forraising catalyst activity. It is an object of the present invention toprovide a concentration distribution for a platinum group metalcomponent in a catalyst with which catalyst activity can be increased,and to provide a method for supporting a platinum group metal with whichthis concentration distribution can be achieved.

As a result of diligent research into the distribution of the platinumgroup metal component in a solid acid catalyst, the inventors discoveredthat the concentration is higher around the outer periphery or isnonuniform in catalyst cross section in the concentration distributionof a platinum group metal component produced by a conventional preparingmethod, and perfected the present invention upon realizing that catalystactivity could be increased by making this distribution uniform.

The solid acid catalyst containing a platinum group metal componentpertaining to the present invention is a solid acid catalyst thatcomprises porous catalyst pellets exhibiting solid acid characteristics,and a platinum group metal component supported by these catalystpellets, and that is used in an acid-catalyzed reaction, in which aquotient of dividing a standard deviation of concentration in theplatinum group metal component concentration distribution in thecatalyst by an average concentration is 0.4 or less. It is preferable ifthe platinum group metal component has been crystallized. It is alsopreferable if the catalyst pellets are composed of a shaped supportconsisting of a metal oxide, and a sulfurous component supported by thissupport. Further, as the metal component, the support preferablyincludes zirconium in an amount of 20 to 72 wt % as elemental zirconiumweight in the catalyst. This solid acid catalyst can be used toadvantage in the isomerization of hydrocarbons containing a saturatedhydrocarbon component having 4 to 10 carbon atoms, preferably asaturated hydrocarbon component having 4 to 6 carbon atoms, in an amountof at least 70 wt %. “Metal oxide” as used in this Specification isdefined as encompassing hydrated metal oxides.

The method for preparing a solid acid catalyst pertaining to the presentinvention comprises a step of preparing a support solution containing aplatinum group metal as a cation, and a step of impregnatingcrystalline, porous catalyst pellets exhibiting solid acidcharacteristics with this support solution. Preferably, the catalystpellets are produced by a step of supporting a sulfureous component on ashaped support consisting of a metal oxide, and the support solutioncontains an ammine complex of a platinum group metal.

If chloroplatinic acid, which forms a platinum group metal anion, isused as the support solution of a platinum group metal and the catalystpellets are impregnated with the support solution, the capillary actionof pores of the porous support will cause the concentration of platinumgroup metal to be higher in the center portion of the pellets, but thesubsequent calcining will result in considerable local variance in theconcentration of the platinum group metal. The reason for this seems tobe that there is no interaction between the anions and the acidicactivity points within the catalyst pellets, so the concentrationdistribution of the platinum group metal tends to vary during drying andcalcining. With the present invention, when the platinum group metal ispresent as cations in impregnation, it selectively reaches the acidicactivity points within the catalyst pellets, and the platinum groupmetal concentration becomes higher around the outer part of thecatalyst. Drying and calcining then result in a uniform distribution ofthe platinum group metal. This uniform support of the platinum groupmetal increases catalyst activity.

Solid Acid Catalyst

The solid acid catalyst of the present invention comprises porouscatalyst pellets exhibiting solid acid characteristics, and a platinumgroup metal component supported by these catalyst pellets, and that isused in an acid-catalyzed reaction, wherein the quotient (hereinafteralso referred to simply as the standard deviation/average) of dividingthe standard deviation of the concentration in the platinum group metalcomponent concentration distribution in said catalyst by the averageconcentration is 0.4 or less. It is preferable if the catalyst pelletsthat exhibit solid acid characteristics are crystalline and porous.

The catalyst of the present invention is in a shaped form known aspellets, rather than a powder, and pellets 0.5 to 20 mm in size can beeasily obtained. Usually, those with an average size of 0.5 to 20 mm,and particularly 0.6 to 5 mm, can be used to advantage. The mechanicalstrength of the catalyst, in terms of the side crushing strength ofcylindrical pellets with a diameter of 1.5 mm, is at least 2 kg, andpreferably at least 3 kg, and even more preferably 4 to 8 kg.

The catalyst pellets of the present invention preferably include ashaped support consisting of a metal oxide. There are no particularrestrictions on the metal component of this metal oxide (including ahydrated metal oxide), but examples include boron, magnesium, aluminum,silicon, phosphorus, calcium, titanium, vanadium, chromium, manganese,iron, cobalt, nickel, copper, zinc, gallium, germanium, yttrium,zirconium, niobium, molybdenum, tin, hafnium, tungsten, lanthanum, andcerium. Aluminum, silicon, titanium, manganese, iron, yttrium,zirconium, molybdenum, tin, hafnium, and tungsten are preferred, andaluminum, titanium, iron, zirconium, and tin are particularly favorable.These metal oxides can be used singly or in mixtures, and can also beused in the form of a composite metal oxide such as a zeolite.

At least part of the metal component of the metal oxide used in thesupport of the present invention is preferably zirconium, and thezirconium content in the catalyst is preferably 20 to 72 wt %, and morepreferably 30 to 60 wt %, as elemental zirconium weight. Also, at leastpart of the metal component of the metal oxide used in the support ofthe present invention is preferably aluminum, and the aluminum contentin the catalyst is preferably 5 to 30 wt %, and more preferably 8 to 25wt %, as elemental aluminum weight. It is particularly favorable thatthe solid acid catalyst of the present invention contains zirconium andaluminum as metal components, and a halogen can be further contained asneeded in order to enhance the acid catalyst performance of the product.

It is preferable that the catalyst pellets of the present inventioncontain a sulfureous component. The proportion of the catalyst accountedfor by the sulfureous component (SO₄) is 0.7 to 7 wt % as elementalsulfur weight, and preferably 1 to 6 wt %, and even more preferably 2 to5 wt %. Catalyst activity will decrease if the content of the sulfureouscomponent is either too large or too small.

One or more metals selected from among platinum group metals arecontained in the solid acid catalyst of the present invention. Exampleof the platinum group metals referred to here include platinum,palladium, ruthenium, rhodium, iridium, and osmium. Platinum, palladium,and ruthenium are preferable, and the use of platinum is particularlyfavorable.

It is preferable for the platinum group metal to have been crystallized.The platinum group metal being crystallized means that there is a cleardiffraction peak for a platinum group metal as measured by powder X-rayanalysis. If we let 100% be the surface area of a diffraction peakproduced by fully crystallized platinum, then the crystallization of theplatinum group metal is confirmed by the appearance of a peak with asurface area of at least 30%, and particularly at least 50%, at the sameposition (hereinafter, the degree of crystallization is referred to as“crystallinity”).

The proportion of the catalyst accounted for by the platinum group metalcomponent (the average platinum group metal component concentration) is0.01 to 10 wt %, and preferably 0.05 to 5 wt %, and especially 0.1 to 2wt %, as the elemental metal weight. It is undesirable for the platinumgroup metal component content to be too low because the improvement incatalyst performance will be small. It is also undesirable for theplatinum group metal component content to be too high because it willlower the specific surface area and pore volume of the catalyst.

The quotient of dividing the standard deviation of the concentration ofthe platinum group metal component concentration in the catalystpertaining to the present invention by the average concentration is 0.4or less, and preferably 0.3 or less. This value can be obtained bydividing up a line that passes through the center of the catalyst crosssection (such as a line corresponding to the diameter in the case of acircular cross section) into at least 50 segments and finding theaverage concentration in each segment,and the standard deviation of themeasured concentrations. The concentration distribution of the platinumgroup metal component can be found as the concentration of the platinumgroup metal component in the catalyst cross section from the measurementof X-ray intensity using an EPMA measurement apparatus. The crystallitediameter of the platinum group metal measured by X-ray diffraction is 10nm or less, with 1 to 10 nm being particularly favorable. The platinumgroup metal concentration will tend to be uniform if the platinum groupmetal component is contained in an amount of at least 0.15 wt %, andparticularly at least 0.2 wt %, and especially at least 0.3 wt %.

The specific surface area of the solid acid catalyst of the presentinvention is 50 to 500 m²/g, with 100 to 300 m²/g being preferable, and140 to 200 m²/g being particularly favorable. The specific surface areacan be measured by the commonly known BET method. The pore structure ofthe solid acid catalyst of the present, invention can be analyzed by anitrogen adsorption method for pore diameters ranging from 0.002 to 0.05μm, and by mercury porosimetry for pore diameters ranging from 0.05 to10 μm. The pore volume at a pore diameter of 0.002 to 10 μm is at least0.2 cm³/g, with at least 0.3 cm³/g being preferable, and 0.35 to 1.0cm³/g being particularly favorable.

Catalyst Preparation Method

The method for preparing a solid acid catalyst of the present inventioncomprises a step of preparing a support solution containing a platinumgroup metal as a cation, and a step of impregnating crystalline, porouscatalyst pellets exhibiting solid acid characteristics with this supportsolution. There are no particular restrictions on the support solutionas long as it contains a platinum group metal as a cation, but one thatcontains an ammine complex of a platinum group metal is preferred. Thisammine complex can be dichlorotetraammine platinum,tetrachlorohexaammine platinum, or the like. Platinum, palladium,ruthenium, and the like are favorable as the metal component selected asthe platinum group metal component, and platinum can be used toparticular advantage. The platinum group metal component may alsoinclude a metal component from another group. It is preferable to addthese metal compounds such that the total amount of the platinum groupmetal component in the solid acid catalyst is 0.01 to 10 wt %, with 0.1to 5 wt % being preferable, and 0.15 or higher being particularlyfavorable. The pH of the support solution should be 5 to 8, with 6 to7.5 being particularly good. Outside this range there will be a relativedecrease in catalyst activity.

There are no particular restrictions on how the impregnation with thesupport solution is accomplished, but methods that can be used includespraying and dipping. After impregnation, the support solution isusually stabilized by drying, calcining, or the like. The calciningtemperature will vary with the calcining time and other calciningconditions, but is generally 300 to 800° C., with 400 to 800° C. beingparticularly good, and 500 to 700° C. being even better. The calciningtime will vary with the calcining temperature and other calciningconditions, but is generally 0.05 to 20 hours, with 0.1 to 10 hoursbeing particularly good, and 0.2 to 5 hours being even better. It ispreferable for the calcining to be performed at the same or highertemperature as in the calcining or other such heat treatment carried outin the preparation of catalyst pellets. The drying and calcining may beconducted in a gas atmosphere of air, nitrogen, or the like, but it ismore desirable that it be conducted in air. Reduction is preferablyperformed in a gas flow containing hydrogen.

There are no particular restrictions on the method for preparing theporous catalyst pellets exhibiting solid acid characteristics, but anexample is a method in which a sulfur-containing compound is added toand kneaded with a powder of a hydrated metal oxide and/or a metalhydroxide, which is a powder that becomes a precursor of the metal oxidethat makes up the support (hereinafter referred to as “precursorpowder”), and this mixture is then shaped and calcined. This method willbe used for the following description, but the order of the calcining ofthe support, the supporting of the sulfureous component, and so forthcan be changed as needed.

Precursor Powder

The precursor powder, which becomes the metal oxide constituting thesupport by calcining after shaping, can be prepared in any way desired,but it can generally be obtained by neutralizing or hydrolyzing a metalsalt or organometal compound, then washing and drying. This precursorpowder can be a mixture of two or more kinds of powder. This precursorpowder can also be a composite metal hydroxide and/or composite metalhydrate oxide.

Sulfur-containing Compound

The sulfur-containing compound is a compound containing sulfureouscomponent, or a compound containing sulfur that can be subsequentlyconverted into a sulfureous component by calcining or another suchtreatment. Examples of sulfur-containing compounds include sulfuricacid, ammonium sulfate, sulfurous acid, ammonium sulfite, thionylchloride, and dimethylsulfuric acid, but the use of a sulfureouscomponent-containing compound is preferable, and ammonium sulfate anddimethylsulfuric acid are favorable because of their low corrosivity tothe preparing equipment. The use of ammonium sulfate is best of all.

The sulfur-containing compound may be used just as it is, or in the formof a solution, such as an aqueous solution. The sulfur-containingcompound may be in the form of a solid or a liquid, and there are noparticular restrictions on the concentration of the solution, which canbe prepared by taking into account such factors as the amount ofsolution needed for kneading. It is preferable to add thesulfur-containing compound such that the amount of the sulfureouscomponent (SO₄) in the ultimately obtained solid acid catalyst be 1 to10 wt %, and preferably 1.5 to 9 wt %, and particularly 2 to 8 wt %, asthe elemental sulfur weight.

Kneading

There are no particular restrictions on the kneading method, and anykneader commonly used in the preparation of catalysts can be employed. Amethod in which the raw material is put into a kneader, and water isadded and mixed with an agitation impeller can usually be used toadvantage, but there are no particular restrictions on the order inwhich the raw materials and additives are introduced and so forth. Wateris usually added during kneading, but the added liquid may instead beethanol, isopropanol, acetone, methyl ethyl ketone, methyl isobutylketone, or another organic solvent. The kneading temperature and timewill vary with the hydrated metal oxide and/or metal hydroxide precursorpowder and sulfur-containing compound as the raw materials, but thereare no particular restrictions as long as the conditions allow afavorable pore structure to be obtained. Similarly, as long as thecatalyst properties of the present invention are maintained, an acidsuch as nitric acid, a base such as ammonia, an organic compound, ametal salt, ceramic fibers, a surfactant, a zeolite, clay, or the likemay also be added and kneaded.

Shaping

There are no particular restrictions on the shaping method employedafter kneading, and any shaping method commonly employed in thepreparation of catalysts can be used. Extrusion shaping using a screwextruder or the like is particularly favorable because it allows thematerial to be efficiently shaped into pellets, a honeycomb shape, orother desired shape. There are no particular restrictions on the size ofthe shaped product, but the cross sectional length thereof is usually0.5 to 20 mm. For instance, cylindrical pellets with a diameter of 0.5to 10 mm and a length of about 0.5 to 15 mm can usually be obtained withease.

Calcining After Shaping

The calcining performed after shaping is conducted in a gas atmosphereof air, nitrogen, or the like, but it is especially favorably conductedin air. The calcining temperature will vary with the calcining time, thegas flux, and other calcining conditions, but is generally 400 to 900°C., and preferably 500 to 800° C. The calcining time will vary with thecalcining temperature, the gas flux, and other calcining conditions, butis generally 0.05 to 20 hours, with 0.1 to 10 hours being preferable,and 0.2 to 5 hours being particularly favorable.

Application to Reaction

The acid-catalyzed reactions to which the solid acid catalyst pertainingto the present invention is applied include acid-catalyzed reactionswhich in the past made use of a Lewis acid catalyst, typified by analuminum chloride-based catalyst, or a Broensted acid catalyst, typifiedby sulfuric acid. The catalyst of the present invention can be used toadvantage in a wide range of reactions, especially isomerization,disproportionation, nitration, decomposition, alkylation,esterification, acylation, etherification, rearrangement,polymerization, and so forth. Specific examples in which the catalyst ofthe present invention can be used include the isomerization of lightnaphtha, isomerization of a wax, isomerization of an olefin,isomerization of xylene, disproportionation of toluene, nitration of anaromatic compound, decomposition of fluorocarbons, decomposition ofcumene hydroperoxide, alkylation of butene and butane, alkylation of anaromatic compound, esterification of methacrylic acid and the like,esterification of phthalic anhydride, acylation of an aromatic compound,etherification of isobutene and methanol, Beckmann rearrangement,ring-opening polymerization of tetrahydrofuran, polymerization of anolefin, and oxidative coupling of methane. The use of the catalyst ofthe present invention is favorable in the isomerization of hydrocarbonsincluding at least 70 wt % saturated hydrocarbon component having 4 to10 carbon atoms, and particularly 4 to 6 carbon atoms.

Hydrocarbon Used in Isomerization Reaction

There are no particular restrictions on the hydrocarbon that serves asthe raw material of the isomerization reaction of the present invention,but the hydrocarbons in a petroleum fraction whose boiling point isbetween −20° C. and 250° C., and particularly between −20° C. and 150°C., can be used favorably. It is preferable to use hydrocarbons in whichsaturated hydrocarbons having 4 to 6 carbon atoms account for at least70 wt %, and particularly at least 90 wt %, of the total. A favorablereaction is one in which a straight-chain paraffin is isomerized into abranched paraffin, or an olefin or an aromatic compound is hydrogenatedinto a linear or cyclic paraffin, and then further isomerized. As to thereaction conditions for the isomerization of hydrocarbon compounds, thepreferred reaction temperature range is from 20 to 300° C., andparticularly 100 to 250° C., the preferred reaction pressure range isfrom 1 to 50 kgf/cm², the preferred LHSV range is from 0.2 to 10/hr, andthe preferred hydrogen/raw material ratio is given so as to provide atleast the amount of hydrogen needed to saturate the unsaturatedcomponent (olefin component, aromatic component) included in the rawmaterial hydrocarbon, and particularly from 0.01 to 10 mol/mol.

If the amount of benzene included in the hydrocarbon serving as the rawmaterial is at least 0.5 wt %, and particularly 2 to 20 wt %, it ispreferable to use a solid acid catalyst pertaining to the presentinvention in which the total amount of platinum group metal componentaccounts for 0.15 to 5 wt %, and preferably 0.2 to 4 wt %, and even morepreferably 0.3 to 3 wt %, of the solid acid catalyst. If the platinumgroup metal content is lower than this range, the benzene that ispresent will hinder the isomerization of the linear or cyclic paraffin,resulting in a relative decrease in the conversion of hydrocarbons.

The amount in which the sulfur compound is contained in the hydrocarbonserving as the raw material in the isomerization reaction of the presentinvention is preferably no more than 500 ppm, and preferably no morethan 100 ppm, and particularly no more than 1 ppm, as the sulfur weight.The amount of water in the hydrocarbon serving as the raw material inthe isomerization reaction of the present invention is preferably nomore than 100 ppm, and preferably no more than 5 ppm, and particularlyno more than 1 ppm.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is the X-ray diffraction pattern of catalyst A obtained inExample 1;

FIG. 2 is the X-ray diffraction pattern of catalyst F obtained inComparative Example 2; and

FIG. 3 is the X-ray diffraction-pattern of a standard catalyst in whichthe crystallinity is 100%.

BEST MODE FOR CARRYING OUT THE INVENTION

Following is a more detailed description through examples.

Method of Measuring Mean Particle Size of Agglomerate of Particles

Measurement was carried out by a wet measurement method using aMicrotrac particle size analyzer made by Nikkiso Co., Ltd. With thismethod, the powder is dispersed in water, a laser beam is irradiatedonto the flowing agglomerated particles, and particle size analysis iscarried out using the forward-scattered light.

Method of Measuring Pore Structure

The specific surface area and the pore structure for a pore diameterrange of 0.002 to 0.05 μm were measured by a nitrogen adsorption methodusing an ASAP 2400 measuring apparatus made by Micromeritics. For a porediameter range of 0.05 to 10 μm, measurement was carried out by mercuryporosimetry using an AutoPore 9200 measuring apparatus made byMicromeritics.

Method of Measuring Mean Crushing Strength

The side crushing strength was measured using a sample obtained byextruding into a cylindrical shape, drying and calcining, using a tabletcrushability tester “TH-203CP” made by Toyama Sangyo Co., Ltd. Ameasuring probe having a circular tip of diameter 4.5 mm was used. Theoperation of carrying out measurement by pushing the measuring sampleagainst the center of the side of the cylindrical sample was repeated 20times, and the mean was calculated.

Analysis of Platinum Component Distribution by EPMA

The platinum concentration was measured at approximately 150 points atintervals of 10 μm in the radial direction of the catalyst cross sectionusing an EPMA measurement apparatus. The concentration was calculated asfollows. The X-ray intensity at the peak of the characteristic X-ray forthe platinum group metal was measured as well as the X-ray intensitiesat the background positions ahead of and behind the peak, the backgroundvalue was determined at the peak position, the background was subtractedfrom the measured intensity at the peak position, and this remainder wastermed the true intensity. Measurement with the EPMA apparatus wasconducted under the following conditions using an EPMA JXA8900R made byJEOL Ltd.

-   -   Acceleration voltage: 20 kV    -   Sample current: 0.1 μA    -   Beam diameter: 10 μmφ    -   Spectroscopic crystal: LiF    -   Measurement energy position (with platinum)        -   PtLα (peak position): 9.441 keV        -   background position: 8.768 keV, 9.817 keV            Catalyst Pellets A

A powder with an average particle size of 1.5 μm and produced by dryingcommercially available dry zirconium hydroxide was used as a hydratedzirconia powder. A commercially available pseudo-boehmite powder with anaverage particle size of 10 μm was used as a hydrated alumina powder.1860 g of this hydrated zirconia powder and 1120 g of hydrated aluminapowder were added, 575 g of ammonium sulfate was further added, and thecomponents were kneaded for 45 minutes in a kneader equipped withagitating blades while water was added. The kneaded product was extrudedfrom an extruder having a circular opening 1.6 mm in diameter, whichformed cylindrical pellets, and these were dried at 110° C. to obtaindry pellets. A portion of these dry pellets was then calcined for 1.5hours at 657° C. to obtain catalyst pellets A.

These shaped catalyst pellets A were cylindrical, with an averagediameter of 1.4 mm and an average length of 4 mm, and their averagecrushing strength was 4.2 kg. The proportion of zirconia in the catalystpellets A was 45.4 wt % as the elemental zirconium weight, theproportion of alumina was 14.7 wt % as the elemental aluminum weight,the proportion of sulfureous component was 3.0 wt % as the elementalsulfur weight, and the proportion of nitrogen was no more than 0.01 wt%. The specific surface area of the catalyst pellets A was 165 m²/g, thepore volume of pores with a diameter of 0.002 to 10 μm was 0.32 mL/g,and the median pore diameter in a pore diameter range of 0.002 to 0.05μm of the catalyst pellets A was 54 Å.

EXAMPLE 1

An aqueous solution (pH 7.0) of dichlorotetraammine platinum((NH₃)₄PtCl₂) was supported on 125 g of Catalyst Pellets A by sprayingsuch that the amount of platinum in the catalyst would be 0.5 wt %. Thisproduct was dried, then calcined for 0.5 hour at 680° C. to obtainapproximately 125 g of Catalyst A (MO-567).

EXAMPLE 2

Catalyst B (MO-673) was obtained in the same manner as in Example 1,except that the amount of platinum in the catalyst was changed to 0.33wt %.

Comparative Example 1

Catalyst C (MO-599) was obtained in the same manner as in Example 1,except that the amount of platinum in the catalyst was changed to 0.11wt %.

EXAMPLE 3

Catalyst D (MO-631) was obtained in the same manner as in Example 1,except that hydrochloric acid was added to the aqueous solution ofdichlorotetraammine platinum to adjust the pH of the support solution to1.8.

EXAMPLE 4

Catalyst E (MO-630) was obtained in the same manner as in Example 1,except that aqueous ammonia was added to the aqueous solution ofdichlorotetraammine platinum to adjust the pH of the support solution to9.6.

Catalysts A to E were the same as the catalyst pellets A in terms oftheir shape, average crushing strength, proportion of zirconia,proportion of alumina, proportion of sulfureous component, and porevolume of pores having a diameter of 0.002 to 10 μm. Tables 1 and 2 showthe standard deviation/average value for the platinum concentration ineach of Catalysts A to E, the platinum crystallite diameter measured byX-ray diffraction, the proportion of the catalyst accounted for bynitrogen, the specific surface area, the median pore diameter in a porediameter range of 0.002 to 0.05 μm, and the sulfureous component content(as the elemental sulfur weight).

Comparative Example 2

An aqueous solution of chloroplatinic acid (H₂PtCl₆) was supported byspraying on 125 g of the catalyst pellets A such that the amount ofplatinum in the catalyst would be 0.5 wt %. This product was dried, thencalcined for 0.5 hour at 680° C. to obtain approximately 125 g ofCatalyst F. The diffusion and distribution of platinum in Catalyst F wasnot uniform, and the standard deviation/average value of platinumconcentration was 0.51. Observation by scanning electron microscoperevealed agglomerated particles of platinum in Catalyst F that were notseen with Catalyst A. The properties of Catalyst F are also shown inTable 2.

TABLE 1 Comp. Example 1 Example 2 Ex. 1 Catalyst Catalyst A Catalyst BCatalyst C pH of support 7.0 7.0 7.0 Platinum concentration 0.5 0.330.11 (wt %) Standard 0.18 0.33 0.86 deviation/average value of platinumconcentration Platinum crystallite 8.0 6.5 7.2 diameter (nm) Nitrogencontent (wt %) ≦0.01 ≦0.01 ≦0.01 Specific surface area 162 158 163(m²/g) Median pore diameter 5.8 6.0 5.7 (nm) Sulfureous component 2.82.7 2.7 content (wt %)

TABLE 2 Comp. Example 3 Example 4 Ex. 2 Catalyst Catalyst D Catalyst ECatalyst F pH of support 1.8 9.6 — Platinum concentration 0.5 0.5 0.5(wt %) Standard 0.20 0.24 0.51 deviation/average value of platinumconcentration Platinum crystallite 7.9 7.9 40 diameter (nm) Nitrogencontent (wt %) ≦0.01 ≦0.01 ≦0.01 Specific surface area 159 159 163(m²/g) Median pore diameter 5.9 6.0 5.6 (nm) Sulfureous component 2.72.8 2.8 content (wt %)

The crystallinity of Catalysts A and F was measured by X-ray diffractionunder the following measurement conditions. FIGS. 1 to 3 show theobtained X-ray diffraction patterns.

(1) X-ray diffraction measurement conditions: An RAD-1C X-raydiffraction apparatus made by Rigaku Denki was used.

-   X-ray tube; sealed copper bulb    -   (tube voltage: 30 kV, tube current: 45 mA, wavelength: 0.15407        nm)-   Measurement region (2θ): 37 to 43°-   Scanning rate: 0.1°/minute-   Step width: 0.01°-   Slit width: divergent slit (DS)=1°    -   scattering slit (SS)=1°    -   receiving slit (RS)=0.03 mm-   Smoothing: 25 times

(2) Diffraction peak used: the peak near 2θ=39.7° (Peaks other than thetarget were separated using “Crystallity (peak separation method)”application software from Rigaku Denki for an X-ray diffractionapparatus, and the peak surface area was found.

(3) Standard sample for crystallinity: This sample was prepared in thesame manner as Catalyst F, except that the calcining after thesupporting of the chloroplatinic acid aqueous solution was performed for12 hours at 800° C.

The crystallinity was calculated from the peak surface area of CatalystsA and F, with the surface area of the peak near 2θ=39.7° of thisstandard sample corresponding to a crystallinity of 100%.

TABLE 3 Peak surface Crystal- Diffraction area linity pattern Catalyst A48.17  66% FIG. 1 Catalyst F 0.29 ≦20% FIG. 2 Standard 73.37 100% FIG. 3sample

EXAMPLE 5 and Comparative Example 3

Light Naphtha Isomerization Reaction

4 cc of catalyst (Catalysts A and F) that had been graded to getgranules passable through a 16 to 24 mesh sieve was charged into a fixedbed reactor with a length of 50 cm and an inside diameter of 1 cm, andpretreatment was followed by the isomerization of light naphtha. Thispretreatment was carried out at a temperature of 400° C., at normalpressure, in an air atmosphere, for 1 hour. After this, the inside ofthe reactor was replaced with a nitrogen atmosphere without allowing airto enter, and the atmosphere was then changed to hydrogen, after whichthe isomerization reaction was commenced.

The desulfurized light naphtha used as the reaction raw materialcontained 5.8 wt % butane, 58.8 wt % pentane, 29.7 wt % hexane, 2.3 wt %cyclopentane, 2.6 wt % methylcyclopentane and cyclohexane, 1.0 wt %benzene, and 0.1 wt % olefin. The water content was no more than 40weight ppm, the sulfur compound concentration was no more than 1 weightppm (as sulfur), the nitrogen compound concentration was no more than0.1 weight ppm (as nitrogen), the concentration of oxygen compoundsother than water was no more than 0.1 weight ppm (as oxygen), and thechlorine compound concentration was no more than 0.1 weight ppm (aschlorine).

The hydrogen gas used in the reaction had a purity of 99.99 vol %, thewater concentration was no more than 0.5 weight ppm, and as for otherimpurities, the sulfur compound concentration was no more than 1 weightppm (as sulfur), the nitrogen compound concentration was no more than0.1 weight ppm (as nitrogen), the concentration of oxygen compoundsother than water was no more than 0.1 weight ppm (as oxygen), and thechlorine compound concentration was no more than 0.1 weight ppm (aschlorine).

The isomerization of light naphtha was carried out at a reactiontemperature of 195°C., a reaction pressure (gauge pressure) of 1.96 MPa(20 kg/cm²), an LHSV of 2/hr, and a hydrogen/oil ratio (H₂/oil) of 2(mol/mol). 200 hours after the start of oil flow, the reaction tubeoutlet composition was analyzed by gas chromatography. Table 4 shows thereaction tube outlet composition (analysis results). iC5/ΣC5 in Table 4is the proportion (wt %) of isopentane in the fraction of C₅straight-chain hydrocarbons, and 2,2′-DMB/ΣC6 is the proportion (wt %)of 2,2′-dimethylbutane in the fraction of C₆ straight-chainhydrocarbons. The i-C5/ΣC5 of the desulfurized light naphtha used as thereaction raw material was 40.1 wt %, and the 2,2′DMB/ΣC6 was 1.4 wt %.

TABLE 4 Catalyst i-C5/ΣC5 2,2′-DMB/ΣC6 Example 5 Catalyst A 73.4 wt %26.3 wt % Comp. Ex. 3 Catalyst F 73.1 wt % 25.0 wt %

EXAMPLES 6 to 9 and Comparative Examples 4 and 5

n-Hexane Isomerization Reaction

The reaction raw material consisted of either raw material 1 (100 wt %n-hexane) or raw material 2 (a mixture of 6 wt % benzene and 94 wt %n-hexane). The water concentration was no more than 40 weight ppm, thesulfur compound concentration was no more than 1 weight ppm (as sulfur),the nitrogen compound concentration was no more than 0.1 weight ppm (asnitrogen), the concentration of oxygen compounds other than water was nomore than 0.1 weight ppm (as oxygen), and the chlorine compoundconcentration was no more than 0.1 weight ppm (as chlorine).

The isomerization of n-hexane was carried out at a reaction temperatureof 180° C., a reaction pressure (gauge pressure) of 0.98 MPa, an LHSV of1.5/hr, and a hydrogen/oil ratio (H₂/oil) of 5 (mol/mol). 70 hours afterthe start of oil flow, the composition at the reaction tube outlet wasanalyzed by gas chromatography. The rest of the reaction conditions werethe same as in the isomerization of light naphtha.

Table 5 shows the n-hexane conversion when Catalysts A, B, C and F wereused, and the amount (wt %) of 2,2′-dimethylbutane contained in thesaturated hydrocarbons having six carbon atoms in the reaction product.The benzene conversion was roughly 100%. The conversion was the same inall of the reactions in which just n-hexane was isomerized, but whenbenzene was contained, it can be seen that the conversion decreaseddepending on the supporting method and the amount of platinum supported.

TABLE 5 Raw material 2: Raw material 1: 6 wt % benzene, Platinum 100 wt% n-hexane 94 wt % n-hexane content Conversion 2,2′-DMB/ Conversion2,2′-DMB/ Catalyst (wt %) (wt %) C6p (wt %) (wt %) C6p (wt %) Ex. 6Catalyst 0.5 85 17.0 80 12.5 A Ex. 7 Catalyst 0.33 85 16.5 80 12.1 B C.E. 4 Catalyst 0.11 85 17.4 58 3.2 C C. E. 5 Catalyst 0.5 85 17.6 67 4.6F [C. E.: Comparative Example]

Table 6 shows the amount (wt %) of the 2,2′-dimethylbutane contained inthe saturated hydrocarbons having six carbon atoms in the n-hexanereaction product when Catalysts D and E were used, along with theresults for Example 6. There is a slight decrease in the amountcontained when the pH of the support solution is not near neutral.

TABLE 6 pH of support 22 DMB/C6p Catalyst solution n-C6 100% Example 6Catalyst A 7.0 17.0 Example 8 Catalyst D 1.8 15.0 Example 9 Catalyst E9.6 15.1

Industrial Applicability

When catalyst pellets impregnated with chloroplatinic acid, which formsa platinum group metal anion, is used as a platinum group metal supportsolution, the capillary action of pores of the porous support causes theconcentration of platinum group metal to be higher in the center portionof the pellets, but the subsequent calcining results in considerablelocal variance in the concentration of the platinum group metal. Thereason for this seems to be that there is no interaction between theanions and the acidic activity point within the catalyst pellets, so theconcentration distribution of the platinum group metal tends to varyduring drying and calcining. With the present invention, when theplatinum group metal is used as a cation in impregnation, it selectivelyreaches the acidic activity point within the catalyst pellets, and theplatinum group metal concentration becomes higher around the outer partof the catalyst. Drying and calcining then result in a uniformdistribution of the platinum group metal. This uniform support of theplatinum group metal increases catalyst activity.

1. A shaped solid acid catalyst that comprises porous catalyst pelletsexhibiting solid acid characteristics, a platinum group metal componentcontained and supported by the catalyst pellets in an amount of at least0.15 wt. % by using a support solution containing a platinum group metalas a cation, in which a quotient of dividing a standard deviation ofconcentration in the platinum group metal component concentrationdistribution in said catalyst by an average concentration is 0.4 or lessand wherein the catalyst pellets are composed of a shaped supportconsisting of a metal oxide, and a sulfureous component supported by thesupport.
 2. The solid acid catalyst according to claim 1, wherein theplatinum group metal component has been crystallized.
 3. The solid acidcatalyst according to claim 1, wherein a metal component of the metaloxide is at least one selected from the group consisting of aluminum,titanium, iron, zirconium and tin.
 4. The solid acid catalyst accordingto claim 3, wherein the metal component of the support includeszirconium and aluminum, and the zirconium and the aluminum are containedin the catalyst in an amount of 20 to 72 wt % as elemental zirconiumweight and in an amount of 5 to 30 wt % as elemental aluminum weight,respectively.
 5. The solid acid catalyst according to claim 1, whereinthe acidcatalyzed reaction is an isomerization reaction of a hydrocarboncontaining at least 70 wt % of a saturated hydrocarbon component having4 to 10 carbon atoms.
 6. The solid acid catalyst according to claim 5,wherein the acid-catalyzed reaction is an isomerization reaction of ahydrocarbon containing at least 0.5 wt % benzene.
 7. A method forisomerizing a hydrocarbon, wherein a hydrocarbon including at least 70wt % of a saturated hydrocarbon component having 4 to 10 carbon atoms isbrought into contact with the solid acid catalyst according to claim 1.8. The isomerization method according to claim 7, wherein thehydrocarbon contains at least 0.5 wt % benzene.
 9. The solid acidcatalyst according to claim 1, wherein the support solution contains anammine complex of a platinum group metal.
 10. The solid acid catalystaccording to claim 9, wherein the support solution containsdichlorotetraammine platinum.
 11. A method for preparing a solid acidcatalyst, comprising a step of preparing crystalline porous catalystpellets by supporting a sulfureous component onto a shaped supportconsisting of a metal oxide, a step of preparing a support solutioncontaining a platinum group metal as a cation, and a step ofimpregnating the crystalline, porous catalyst pellets exhibiting solidacid characteristics with the support solution so that the platinumgroup metal component concentration in the catalyst is at least 0.15 wt.%, a quotient of dividing a standard deviation of concentration in aplatinum group metal component concentration distribution in saidcatalyst by an average concentration is 0.4 or less.
 12. The method forpreparing a solid acid catalyst according to claim 11, wherein theplatinum group metal component is crystallized.
 13. The method forpreparing a solid acid catalyst according to claim 11, wherein the metalcomponent of the support includes zirconium and aluminum, and thezirconium and the aluminum are contained in the catalyst in an amount of20 to 72 wt % as elemental zirconium weight and in an amount of 5 to 30wt % as elemental aluminum weight.
 14. The method forpreparing a solidacid catalyst according to claim 11, wherein the support solutioncontains an ammine complex of a platinum group metal.
 15. The method ofpreparing a solid acid catalyst according to claim 14, wherein thesupport solution contains dichlorotetraammine platinum.
 16. The methodfor preparing a solid acid catalyst according to claim 11 wherein the pHof the support solution is 5 to 8.